Prepare the Chicken: Adjust oven rack to the middle position; preheat to 200°F (93ºC). In a shallow dish, whisk together flour (1/2 cup), salt (1/2 teaspoon), pepper (1/4 teaspoon), Italian seasoning (1/2 teaspoon), and Parmesan (1/4 cup). Pound the thicker ends of chicken to 1/4-inch thickness, then pat dry.
Dredge and Sear: Dredge chicken in the seasoned flour, shaking off excess. Heat 1 tablespoon oil and 1 tablespoon butter in a large skillet over medium-high heat until the butter foams. Cook chicken in batches, 3–4 minutes per side, until golden and just cooked through. Transfer to a plate and keep warm in the oven.
Cook Pancetta and Mushrooms: Add the remaining 1 tablespoon oil to the same skillet. Sauté pancetta (4 ounces) for 2 minutes until fat begins to render. Add mushrooms (8 ounces) (don’t salt yet) and cook 7–8 minutes, stirring occasionally, until browned and fond develops. Adjust the heat if needed to prevent burning or the fond darkening too much.
Build the Sauce: Stir in tomato paste (1 tablespoon); cook 1 minute until deepened in color. Add the garlic (4 cloves) and cook just until fragrant, about 30 seconds — be careful not to let it brown. Pour in the Marsala wine (1 3/4 cups) (and chicken broth, if using), scraping up any browned bits from the bottom of the pan. Bring to a simmer and cook until the liquid reduces and thickens slightly, 7–8 minutes.
Finish the Dish: Stir in lemon juice (2 tablespoons) and any accumulated chicken juices. Lower heat and whisk in cold butter (3 tablespoons), one piece at a time, until glossy and emulsified. Return chicken to the pan, spooning sauce over to coat.
Garnish and Serve: Remove from heat and stir in the parsley (2 tablespoons). Taste and adjust seasoning with salt and pepper as needed. Serve warm with extra sauce spooned over the chicken.
Notes
Brown the chicken in batches. Overcrowding steams instead of sears — and we want that golden crust!
Deglaze smartly. When you pour in the wine, scrape every flavorful bit from the pan. That’s pure flavor gold.
Let the sauce reduce gently. You’re aiming for a glossy, spoon-coating consistency.
Adjust balance at the end. If the sauce leans sweet, add a pinch of salt or a squeeze of lemon.
Add butter off the heat. It melts in gently, giving a velvety texture instead of an oily finish.